The invention relates to apparatus for damping vibrations, especially torsional vibrations between the output element (e.g., a crankshaft) of an engine and the power train in a motor vehicle. More particularly, the invention relates to improvements in apparatus of the type having at least two flywheels which are rotatable relative to each other against the opposition of damper means wherein one flywheel is the input member and the other flywheel is the output member of the damper means. The output member can be coupled to the power train by a clutch, particularly a friction clutch.
Heretofore known vibration damping apparatus of the above outlined type employ dampers which have energy storing elements acting in the circumferential direction of the flywheels and normally including coil springs which store elastic energy, and additional energy storing elements which act in the axial direction of the flywheels and cooperate with friction pads and/or linings to produce friction (i.e., hysteresis). The means for generating friction operate in parallel with energy storing means which act in the circumferential direction of the flywheels.
It has been found that certain conventional vibration damping apparatus can operate satisfactorily (i.e., they are capable of damping torsional vibrations as well as noise) but only under specific circumstances. Thus, the mode of operation of such conventional apparatus is not entirely satisfactory under many operating conditions because their design is a compromise due to an attempt to ensure satisfactory or acceptable operation under a variety of different conditions. For example, a purely mechanical solution does not suffice to cover a wide spectrum of operating conditions entailing the development of many basically different stray movements and noise levels. Moreover, purely mechanical solutions are quite expensive, especially if they are to adequately suppress stray movements and noise under a variety of different operating conditions. This is due to the fact that, if a mechanically operated vibration damping apparatus is to counteract a wide range of amplitudes of undesirable stray movements of the flywheels relative to each other, such undertaking greatly increases the cost, bulk, complexity and sensitivity of the apparatus. Moreover, even a very complex and expensive mechanical vibration damping apparatus is incapable of operating satisfactorily under any one of a wide range of different operating conditions because the individual damper stages (i.e., hystereses produced by individual energy storing elements which act in the circumferential direction of the flywheels) cannot be altered as a function of changes in operating conditions. Still further, presently known apparatus are subject to extensive wear so that their useful life is relatively short, and they are also prone to malfunction.
An object of the invention is to provide a vibration and noise damping apparatus whose versatility exceeds that of heretofore known apparatus and which can be used in a wide variety of systems for transmission of torque, especially between the engines and power trains of motor vehicles.
Another object of the invention is to provide an apparatus whose damping characteristics (i.e., the rate of energy dissipation) can conform to the vibration and/or noise generating behavior of motor vehicles under a wide variety of different operating conditions and/or other influences.
A further object of the invention is to provide an apparatus which can be used to connect existing engines or other prime movers with existing power trains.
An additional object of the invention is to provide an apparatus which operates properly at low or high rotational speeds as well as at resonance RPM and during starting or stoppage of the engine in a motor vehicle.
Still another object of the invention is to provide an apparatus which can properly prevent transmission of undesirable stray movements between an engine and a power train under a variety of apparently contradictory or conflicting circumstances without affecting the quality, reliability and/or reproducibility of the vibration- and/or noise-suppressing action.
Another object of the invention is to provide a relatively simple, compact and inexpensive apparatus which can be readily assembled or taken apart and whose useful life is eminently satisfactory for utilization between the engines and power trains of motor vehicles of all or nearly all kinds.
An additional object of the invention is to provide an apparatus which comprises a relatively small number of relatively simple and inexpensive parts and wherein the percentage of components which need not undergo secondary treatment in material removing tools and the like is higher than in heretofore known apparatus.
A further object of the invention is to provide an apparatus wherein the wear upon the parts which move relative to each other is not pronounced and whose utilization entails minimal losses in the driving system.
Another object of the invention is to provide novel and improved flywheels for use in the above outlined apparatus.
A further object of the invention is to provide a novel and improved method of broadening the range of utility of apparatus for counteracting vibrations and the transmission of noise between the engines and power trains of motor vehicles.
An additional object of the invention is to provide a motor vehicle which embodies the above outlined apparatus.
A further object of the invention is to provide the apparatus with novel and improved means for suppressing stray movements of several flywheels which are rotatable relative to each other and serve to transmit torque between a prime mover and a transmission or the like.
Still another object of the invention is to provide the apparatus with novel and improved means for damping stray movements of several flywheels with reference to each other.
A further object of the invention is to provide an apparatus which can generate a variety of damping actions, either simultaneously or during selected stages of transmission of torque between a prime mover and a power train or the like.
An additional object of the invention is to provide an apparatus wherein a highly satisfactory damping action can be generated by the medium which is used to prolong the useful life of moving parts.
A further object of the invention is to provide the apparatus with novel and improved means for transmitting torque between its components in such a way that the components can be readily separated, reassembled and inspected in a time-saving operation.
Another object of the invention is to provide the apparatus with novel and improved means for varying the vibration- and/or noise-damping action in automatic response to changes in operating conditions.
The invention is embodied in an apparatus for damping vibrations, especially between an engine and a power train. The apparatus comprises a composite flywheel including a first flywheel which is connectable with the engine (e.g., with a crankshaft which is driven by the engine) and a second flywheel which is connectable with the power train (e.g., by way of a friction clutch which is installed between the second flywheel and the input shaft of a change-speed transmission of the power train). The flywheels are rotatable relative to each other against the opposition of damper means which operates between the flywheels, the first flywheel constituting the input member and the second flywheel constituting the output member of the damper means. One of the first and second flywheels includes or carries a housing which defines at least one annular compartment having a substantially closed (e.g., substantially circular) cross-sectional outline. The damper means includes at least one damper having a plurality of deformable energy storing elements (such as coil springs) which are installed in the compartment, and the housing preferably closely conforms to the outlines of the energy storing elements (i.e., the energy storing elements of the one damper are snugly received in the compartment). The one damper further comprises means for deforming the energy storing elements in the compartment, and such deforming means includes first abutment means provided on the housing and located in the compartment and a deforming member (hereinafter called flange for short) which is rotatable with the other of the first and second flywheels and has second abutment means in the compartment. Still further, the damper means comprises a supply of viscous fluid medium (such as a paste) which at least partially fills the compartment.
The flange and the housing can define a narrow gap which communicates with the compartment, and the second abutment means preferably extends substantially radially of the one flywheel. The second abutment means can include radially outwardly extending arms which are integral parts of the flange and form an annulus in a plane making an angle of 90 degrees with the axes of the flywheels. At least one of the arms can include an extension which is disposed in the compartment radially outwardly of the adjacent energy storing element or elements and is preferably received in a portion of the compartment so that its inner side is adjacent the radially outermost portion or portions of the adjacent energy storing element(s).
The housing can include two substantially shell-shaped parts or sections and at least one of these sections can consist of a deformable (ductile) metallic sheet material which can be shaped in a press or a like machine. Each section can constitute a half shell.
The compartment is or can constitute a circumferentially complete annulus, and the first abutment means can constitute discrete stops in the compartment. Such stops can be riveted, welded or otherwise fixedly secured to the respective sections of the housing to alternate with the second abutment means (such as the aforementioned arms of the flange) in the neutral position of the one damper.
At least those portions of the abutment means which actually contact the energy storing elements can have a pronounced hardness. Such pronounced hardness can be achieved as a result of thermal treatment of the aforementioned portions of the abutment means. Alternatively or in addition to such thermal treatment, selected portions of the abutment means and/or of the energy storing elements and/or of the sections of the housing can be provided with coatings of a material which exhibits a pronounced hardness.
The first abutment means can be integral with the housing; for example, such integral first abutment means can include pockets which are provided on one or both sections of the housing and extend into the compartment.
The apparatus can comprise separately produced means for reducing frictional engagement of the housing with the energy storing elements, and such means is preferably disposed radially outwardly of the energy storing elements in the compartment and can include at least one insert in the form of a strip or band of steel or the like. The insert or inserts is or are received in suitable recess(es) of the housing. For example, the entire frictional engagement reducing means can include a single steel band whose end portions are anchored in the housing and whose material exhibits a pronounced hardness.
The band can have a concave side which faces the energy storing elements in the compartment and extends along an arc of 45-120 degrees, preferably along an arc of 60-90 degrees in the circumferential direction of the normally circular cross-sectional outline of the compartment.
The apparatus can further comprise retainer means interposed between at least one of the abutment means and the energy storing elements, particularly between the energy storing elements and the second abutment means. Each retainer means can have an outline which closely conforms to that of the surfaces forming part of the housing and bounding the compartment. The energy storing elements are preferably springs (such as coil springs) having hollow end portions and at least one of the retainer means has an extension in the end portion of the adjacent spring. Such extension can have a substantially conical shape to be readily receivable in the end portion of the adjacent spring. The conicity of the extension can be such that it automatically reenters the end portion of the adjacent spring upon each separation of such end portion from the extension in response to subsequent movement of the end portion of the spring toward the extension and/or vice versa. Each retainer means can act not unlike a piston for the fluid medium in the compartment, and at least one of the retainer means can define a path for the flow of fluid medium therethrough (e.g., through an opening or hole or notch or recess in the retainer means) substantially in the circumferential direction of the flywheels.
The compartment can have a varying cross-sectional area in the region of at least one energy storing element to influence the flow restricting action of the housing in such region and hence the damping action of the damper as a result of different resistance to the flow of fluid medium.